Method of processing positioning data

ABSTRACT

A server arranged to process GPS data to generate enhanced map data is disclosed, and comprises a plurality of navigable segments representing segments of a navigable route in an area covered by a map, the server connected with a wireless telecommunications transceiver arranged to receive GPS fixes by wireless telecommunication from a plurality of navigation devices and send the received GPS fixes to the server, the server comprising a processor arranged to generate at least one speed profile for each segment from the GPS fixes from at least two of the plurality of navigation devices, each speed profile comprising an expected speed of travel through the segment, and the server arranged to subsequently cause the transceiver to send the speed profiles to the navigation devices.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 12/734,256, which claims the benefit ofInternational (PCT) Application No. PCT/EP2008/064318 filed 22 Oct.2008, and which claims priority from U.S. Provisional Patent ApplicationNos. 60/996,050 and 60/996,052, both filed 26 Oct. 2007. The entirecontent of each of these applications is incorporated herein byreference.

FIELD OF THE INVENTION

The invention relates to a method of processing positioning data and inparticular to processing positioning data in order to generate map dataarranged to be used in navigation devices and in particular, but notespecially in a Portable Navigation Device (PND). The invention alsoprovides related apparatus for providing the method.

BACKGROUND OF THE INVENTION

Map data for electronic navigation devices, such as GPS based personalnavigation devices like the GO™ from TomTom International BV, comes fromspecialist map vendors such as Tele Atlas NV. Such devices are alsoreferred to as Portable Navigation Devices (PND's). This map data isspecially designed to be used by route guidance algorithms, typicallyusing location data from the GPS system. For example, roads can bedescribed as lines—i.e. vectors (e.g. start point, end point, directionfor a road, with an entire road being made up of many hundreds of suchsegments, each uniquely defined by start point/end point directionparameters). A map is then a set of such road vectors, data associatedwith each vector (speed limit; travel direction, etc.) plus points ofinterest (POIs), plus road names, plus other geographic features likepark boundaries, river boundaries, etc., all of which are defined interms of vectors. All map features (e.g. road vectors, POIs etc.) aretypically defined in a co-ordinate system that corresponds with orrelates to the GPS co-ordinate system, enabling a device's position asdetermined through a GPS system to be located onto the relevant roadshown in a map and for an optimal route to be planned to a destination.

To construct this map database, Tele Atlas starts with basic roadinformation from various sources, such as the Ordnance Survey for roadsin England. It also has a large, dedicated team of vehicles driving onroads, plus personnel checking other maps and aerial photographs, toupdate and check its data. This data constitutes the core of the TeleAtlas map database. This map database is being continuously enhancedwith geo-referenced data. It is then checked and published four times ayear to device manufacturers like TomTom.

Each such road segment has associated therewith a speed parameter forthat road segment which gives an indication of the speed at which avehicle can travel along that segment and is an average speed generatedby the party that produced the map data, which may be, for example, TeleAtlas. The speed parameter is used by route planning algorithms on PND'son which the map is processed. The accuracy of such route planning thusdepends on the accuracy of the speed parameter. For example, a user isoften presented with an option on his/her PND to have it generate thefastest route between the current location of the device and adestination. The route calculated by the PND may well not be the fastestroute if the speed parameters are inaccurate.

It is known that parameters such as density of traffic can significantlyeffect the speed profile of a segment of road and such speed profilevariations mean that the quickest route between two points may notremain the same. Inaccuracies in the speed parameter of a road segmentcan also lead to inaccurate Estimated Times of Arrival (ETA) as well asselection of a sub-optimal quickest route.

Tele Atlas have developed a system in which GPS data is uploaded fromPND's and used to provide speed parameters for segments of the map datawhich aims to provide speed parameters which show the true speed on aroad segment at predetermined times of a day.

SUMMARY OF THE INVENTION

According to a first aspect of the invention there is provided a serverarranged to process GPS data to generate map data comprising a pluralityof navigable segments representing segments of a navigable route in anarea covered by a map, the server connected with a wirelesstelecommunications transceiver arranged to receive GPS fixes by wirelesstelecommunication from a plurality of navigation devices and send thereceived GPS fixes to the server, the server comprising a processorarranged to generate at least one speed profile for each segment fromthe GPS fixes from at least two of the plurality of navigation devices,each speed profile comprising an expected speed of travel through thesegment, and the server arranged to subsequently cause the transceiverto send the speed profiles to the navigation devices.

The server may be advantageous because it allows the speed profilesassociated with each navigable segment in the area covered by the mapdata to be up-dated wirelessly, in particular the map data on thenavigation devices can be up-dated in “real-time”, i.e. while thenavigation device is providing instructions for a determined route.Real-time updates of the map data may provide the navigation device witha better indication of the traffic flow along that road segment than theold map data, which may well increase the accuracy of routing algorithmsto determine a journey across the area represented by the map data.

The speed profile may be an average speed of travel of navigationdevices, including the plurality of navigation devices, through thesegment. The speed profile may be an average speed that navigationdevices have travelled through the segment in a predetermined timeperiod, for example during the last hour. In this way, the speed profilemay provide an indication of the current traffic behaviour.

According to a second aspect of the invention there is provided a methodof processing GPS data to generate map data comprising a plurality ofnavigable segments representing segments of a navigable route in an areacovered by the map, the method comprising transmitting GPS fixes from aplurality of navigation devices by wireless telecommunication to aprocessor, causing a processor to generate at least one speed profilefor each segment from the GPS fixes from at least two of the pluralityof navigation devices, each speed profile comprising an expected speedof travel through the segment, and sending the speed profiles to thenavigation devices by wireless telecommunications.

According to a third aspect of the invention there is provided anavigation device for determining a route across an area, the navigationdevice comprising a wireless telecommunications transceiver, memoryhaving stored thereon map data comprising a plurality of navigablesegments representing segments of a navigable route in the area coveredby the map data, at least one of the navigable segments has associatedtherewith a speed profile, and a processor arranged to calculate anavigable route using the map data and, in response to at least oneupdated speed profile being received via the transceiver and if thenavigation device is providing routing instructions for the calculatednavigable route, recalculate the navigable route using the at least oneupdated speed profile.

The navigation device may be advantageous as the determined navigableroute is recalculated to take into account any changes in the speedprofiles for segments of the map data on which the route is based. Thismay increase the accuracy of routing algorithms to determine a journeyacross the area represented by the map data.

The navigation device may comprise a positioning device for determiningposition fixes for the navigation device, the processor arranged to sendthe position fixes to a server over a telecommunications network via thetransceiver such that the server can identify routes the navigationdevice has travelled. The positioning device may be a GPS device thatgenerates GPS fixes. In this way, the navigation device can provideposition data to the server on the move. This may allow the server tocalculate speed profiles that are representative of the current trafficbehaviour.

The processor may be arranged to identify segments within apredetermined distance of a current position of the navigation deviceand to change the speed profile for the identified segments to the orone of the updated speed profiles. The predetermined distance may besegments within a particular area around the navigation device, forexample a substantially rectangular or circular shaped area around thenavigation device. The distance between the navigation device and anedge of the area may be of the order of tens or hundreds of kilometers,preferably between 50 and 200 km. The processor may not change the speedprofiles of segments outside of the predetermined distance of thecurrent position of the navigation device to the updated speed profile.By the processor only changing the speed profiles for segments within apredetermined distance of the navigation device, the amount ofprocessing that is required is reduced relative to changing all of thespeed profiles. Only changing the speed profiles for segments within apredetermined distance of the navigation device may not affect theaccuracy of the route determined as a vehicle/person with which thenavigation device is travelling is unlikely to travel to segmentsoutside of the predetermined distance during the time which the updatedspeed profile is relevant.

For example, the updated speed profile may be provided to take accountof a sudden drop in average speeds through segments due to an accidentand the navigation device only needs to change the speed profile for theeffected segments if the navigation device will travel on those segmentswhilst they are affected by the accident. It is likely that if thenavigation device is in a vehicle, such as a car, the effects of anaccident on segments hundreds of kilometers from the current position ofthe vehicle will clear before a vehicle reaches these segments.Accordingly, if the route determined by the navigation device is for amotorised vehicle, the predetermined distance may be of the order tohundreds of kilometers, for example 100 to 200 km. If the routedetermined by the navigation device is for a non-motorised vehicle, suchas a bicycle, then the predetermined distance may be of the order totens of kilometers.

The processor may be arranged to determine the predetermined distancefrom a current speed at which the navigation device is travelling. Forexample, the predetermined distance may be the current speed of thenavigation device multiplied by a preset time, for example one or morehours. The preset time may be a typical time for the traffic behaviourto return to normal after an unusual event, such as a traffic accident.Alternatively, the preset time may be an estimated time for which theupdated profile applies sent to the navigation device, for example bythe server.

In another embodiment, the predetermined distance is based on thebandwidth for the transmission of signals between the navigation deviceand a server that provides the updated speed profile. In this way, abalance may be automatically determined between accuracy of the speedprofiles of the map data and the quantity of data sent to the navigationdevice. Accordingly, in one embodiment, the navigation device may onlyreceive updated speed profiles for segments within the predetermineddistance of the current position of the navigation device.

According to a fourth aspect of the invention there is provided anavigation device for the determination a route, the navigation devicecomprising a wireless telecommunications transceiver, memory havingstored thereon map data, a GPS receiver and a processor arranged to sendGPS fixes obtained by the GPS receiver to a server via the wirelesstelecommunication transceiver and calculate navigable routes using themap data, on request from a user.

In this way, the navigation device can provide GPS fixes to a server inreal-time, or at least pseudo real time, such that a server cancalculate speed profiles for map data and the device can calculatenavigable routes.

According to a fifth aspect of the invention there is provided a datacarrier containing instructions, which when read by a processor of aserver, the server comprising a wireless telecommunications transceiverand the processor, cause the processor to operate in accordance with thefirst aspect of the invention.

According to a sixth aspect of the invention there is provided a datacarrier containing instructions, which when read by a processor of anavigation device cause the navigation device to operate in accordancewith the third or fourth aspects of the invention.

The navigable segments generally represent segments of a road but mayalso represent segments of any other path, channel or the like navigableby a vehicle, person or the like. For example, a navigable segment mayrepresent a segment of a path, river, canal, cycle path, tow path, railway line, or the like.

Reference is made herein to speed data being associated with a roadsegment. The skilled person will appreciate that each road segment isrepresented by data within the map data providing the map. In someembodiments, such data representing the road segment may include anidentifier which provides a reference to the speed data. For example thereference may provide a reference to a generated speed profile. Thisreference may be provided in the form of a look-up table.

In any of the above aspects of the invention the machine readable mediummay comprise any of the following: a floppy disk, a CD ROM, a DVDROM/RAM (including a −R/−RW and +R/+RW), a hard drive, a memory(including a USB memory key, an SD card, a Memorystick™, a compact flashcard, or the like), a tape, any other form of magneto optical storage, atransmitted signal (including an Internet download, an FTP transfer,etc), a wire, or any other suitable medium.

BRIEF DESCRIPTION OF THE DRAWINGS

At least one embodiment of the invention will now be described, by wayof example only, with reference to the accompanying drawings, in which:

FIG. 1 is a schematic illustration of an exemplary part of a GlobalPositioning System (GPS) usable by a navigation device;

FIG. 2a is a schematic diagram of a communications system forcommunication between a navigation device and a server;

FIG. 2b is a schematic diagram of a communication system forcommunication between a plurality of navigation devices and a server;

FIG. 3 is a schematic illustration of electronic components of thenavigation device of FIG. 2a or any other suitable navigation device;

FIG. 4 is a schematic diagram of an arrangement of mounting and/ordocking a navigation device;

FIG. 5 is a schematic representation of an architectural stack employedby the navigation device of FIG. 3.

FIG. 6 shows a flowchart outlining an embodiment for matching GPS fixeswithin a trace to a map;

FIG. 7 shows a flowchart outlining an embodiment for generating speedprofiles; and

FIG. 8 shows a flowchart outlining an embodiment for using updated speedprofiles.

DETAILED DESCRIPTION OF EMBODIMENT OF THE INVENTION

Throughout the following description identical reference numerals willbe used to identify like parts.

Embodiments of the present invention will now be described withparticular reference to a Portable Navigation Device (PND). It should beremembered, however, that the teachings of the present invention are notlimited to PNDs but are instead universally applicable to any type ofprocessing device that is configured to execute navigation software in aportable manner so as to provide route planning and navigationfunctionality. It follows therefore that in the context of the presentapplication, a navigation device is intended to include (withoutlimitation) any type of route planning and navigation device,irrespective of whether that device is embodied as a PND, a vehicle suchas an automobile, or indeed a portable computing resource, for example aportable personal computer (PC), a mobile telephone or a PersonalDigital Assistant (PDA) executing route planning and navigationsoftware.

Further, embodiments of the present invention are described withreference to road segments. It should be realised that the invention mayalso be applicable to other navigable segments, such as segments of apath, river, canal, cycle path, tow path, rail way line, or the like.For ease of reference these are commonly referred to as a road segment.

It will also be apparent from the following that the teachings of thepresent invention even have utility in circumstances, where a user isnot seeking instructions on how to navigate from one point to another,but merely wishes to be provided with a view of a given location. Insuch circumstances the “destination” location selected by the user neednot have a corresponding start location from which the user wishes tostart navigating, and as a consequence references herein to the“destination” location or indeed to a “destination” view should not beinterpreted to mean that the generation of a route is essential, thattravelling to the “destination” must occur, or indeed that the presenceof a destination requires the designation of a corresponding startlocation.

With the above provisos in mind, the Global Positioning System (GPS) ofFIG. 1 and the like are used for a variety of purposes. In general, theGPS is a satellite-radio based navigation system capable of determiningcontinuous position, velocity, time, and in some instances directioninformation for an unlimited number of users. Formerly known as NAVSTAR,the GPS incorporates a plurality of satellites which orbit the earth inextremely precise orbits. Based on these precise orbits, GPS satellitescan relay their location, as GPS data, to any number of receiving units.However, it will be understood that Global Positioning systems could beused, such as GLOSNASS, the European Galileo positioning system, COMPASSpositioning system or IRNSS (Indian Regional Navigational SatelliteSystem).

The GPS system is implemented when a device, specially equipped toreceive GPS data, begins scanning radio frequencies for GPS satellitesignals. Upon receiving a radio signal from a GPS satellite, the devicedetermines the precise location of that satellite via one of a pluralityof different conventional methods. The device will continue scanning, inmost instances, for signals until it has acquired at least threedifferent satellite signals (noting that position is not normally, butcan be determined, with only two signals using other triangulationtechniques). Implementing geometric triangulation, the receiver utilizesthe three known positions to determine its own two-dimensional positionrelative to the satellites. This can be done in a known manner.Additionally, acquiring a fourth satellite signal allows the receivingdevice to calculate its three dimensional position by the samegeometrical calculation in a known manner. The position and velocitydata can be updated in real time on a continuous basis by an unlimitednumber of users.

As shown in FIG. 1, the GPS system 100 comprises a plurality ofsatellites 102 orbiting about the earth 104. A GPS receiver 106 receivesGPS data as spread spectrum GPS satellite data signals 108 from a numberof the plurality of satellites 102. The spread spectrum data signals 108are continuously transmitted from each satellite 102, the spreadspectrum data signals 108 transmitted each comprise a data streamincluding information identifying a particular satellite 102 from whichthe data stream originates. The GPS receiver 106 generally requiresspread spectrum data signals 108 from at least three satellites 102 inorder to be able to calculate a two-dimensional position. Receipt of afourth spread spectrum data signal enables the GPS receiver 106 tocalculate, using a known technique, a three-dimensional position.

Turning to FIG. 2a , a navigation device 200 (ie a PND) comprising apositioning device, in this embodiment a GPS receiver device 106, and awireless transceiver, comprising transmitter 165 and receiver 168,capable of establishing a data session with network hardware of atelecommunications network, such as a cellular network. The wirelesscommunication may be infrared communications, radio frequencycommunications, such as microwave frequency communications, satellitecommunication, etc.

Thereafter, through the telecommunications network, the device 200 canestablish a communication channel 152 (which also may involve othernetworks in addition to the telecommunications network, such as theInternet for example) with a server 150. As such, a wireless networkconnection can be established between the navigation device 200 (whichcan be, and often times is, mobile as it travels alone and/or in avehicle) and the server 150 to provide a “real-time” or at least very“up to date” gateway for information.

The navigation device 200 may utilise “mobile phone technology” withinthe navigation device 200, such as an inbuilt GPRS modem, and caninclude internal components, and/or an insertable card (e.g. SubscriberIdentity Module (SIM) card), complete with necessary mobile phonetechnology and/or an antenna.

The establishing of the network connection between the navigation device200 and the server 150, using the Internet for example, can be done in aknown manner. In this respect, any number of appropriate datacommunications protocols can be employed, for example the TCP/IP layeredprotocol. Furthermore, the navigation device can utilize any number ofcommunication standards such as CDMA2000, GSM, IEEE 802.11 a/b/c/g/n,etc.

The communication channel 152 is not limited to a particulartelecommunications communication technology. Additionally, thecommunication channel 152 is not limited to a single wirelesscommunication technology; that is, the channel 152 may include severalcommunication links that use a variety of technology. For example, thecommunication channel 152 can be adapted to provide a path forelectrical, optical, and/or electromagnetic communications, etc as wellas the wireless communication. Furthermore, the communication channel152 can include intermediate devices such as routers, repeaters,buffers, transmitters, and receivers, for example.

In one illustrative arrangement, the communication channel 152 includestelephone and computer networks.

The communication signals transmitted through the communication channel152 include, but are not limited to, signals as may be required ordesired for given communication technology. For example, the signals maybe adapted to be used in cellular communication technology such as TimeDivision Multiple Access (TDMA), Frequency Division Multiple Access(FDMA), Code Division Multiple Access (CDMA), Global System for MobileCommunications (GSM), General Packet Radio Service (GPRS), etc. Bothdigital and analogue signals can be transmitted through thecommunication channel 152. These signals may be modulated, encryptedand/or compressed signals as may be desirable for the communicationtechnology.

The server 150 includes, in addition to other components which may notbe illustrated, a processor 154 operatively connected to a memory 156and further operatively connected, via a wired or wireless connection158, to a mass data storage device 160. The mass storage device 160contains a store of navigation data and map information, and can againbe a separate device from the server 150 or can be incorporated into theserver 150. The processor 154 is further operatively connected totransmitter 162 and receiver 164, to transmit and receive information toand from navigation device 200 via communications channel 152. Thesignals sent and received may include data, communication, and/or otherpropagated signals. The transmitter 162 and receiver 164 may be selectedor designed according to the communications requirement andcommunication technology used in the communication design for thenavigation system 200. Further, it should be noted that the functions oftransmitter 162 and receiver 164 may be combined into a singletransceiver.

As mentioned above, the navigation device 200 can be arranged tocommunicate with the server 150 through communications channel 152,using transmitter 166 and receiver 168 to send and receive signalsand/or data through the communications channel 152, noting that thesedevices can further be used to communicate with devices other thanserver 150. Further, the transmitter 166 and receiver 168 are selectedor designed according to communication requirements and communicationtechnology used in the communication design for the navigation device200 and the functions of the transmitter 166 and receiver 168 may becombined into a single transceiver as described above in relation toFIG. 2a . Of course, the navigation device 200 comprises other hardwareand/or functional parts, which will be described later herein in furtherdetail.

Software stored in server memory 156 provides instructions for theprocessor 154 and allows the server 150 to provide services to thenavigation device 200. One service provided by the server 150 involvesprocessing requests from the navigation device 200 and transmittingnavigation data from the mass data storage 160 to the navigation device200. Another service that can be provided by the server 150 includesprocessing the navigation data using various algorithms for a desiredapplication and sending the results of these calculations to thenavigation device 200.

The server 150 constitutes a remote source of data accessible by thenavigation device 200 via a wireless channel. The server 150 may includea network server located on a local area network (LAN), wide areanetwork (WAN), virtual private network (VPN), etc.

The navigation device 200 may be provided with information from theserver 150 via information downloads which may be updated automatically,from time to time, or upon a user connecting the navigation device 200to the server 150 and/or may be more dynamic upon a more constant orfrequent connection being made between the server 150 and navigationdevice 200 via the wireless connection. For many dynamic calculations,the processor 154 in the server 150 may be used to handle the bulk ofprocessing needs, however, a processor (not shown in FIG. 2a ) of thenavigation device 200 can also handle much processing and calculation,oftentimes independent of a connection to a server 150.

Referring to FIG. 2b , the server 150 is arranged to communicate with aplurality of navigation devices 200 a to 200 i over, in this embodiment,a cellular telecommunications network 300 and the Internet 301. Eachnavigation device 200 a to 200 i corresponds to the navigation device200, described with reference to FIG. 2a , and has a GPS receiver forobtaining GPS position fixes. In this embodiment, the navigation devices200 a to 200 i communicate with base stations 300 a to 300 c of atelecommunications network 300 and these base stations 300 a to 300 csubsequently pass signals received from the navigation servers 200 a to200 i to server 150 via the Internet 301. Equally, the server 150 iscapable of sending signals to each of the navigation devices 200 a to200 i via the Internet 301 and an appropriate base station 300 a to 300c.

Referring to FIG. 3, it should be noted that the block diagram of thenavigation device 200 is not inclusive of all components of thenavigation device, but is only representative of many examplecomponents. The navigation device 200 is located within a housing (notshown). The navigation device 200 includes processing circuitrycomprising, for example, the processor 202 mentioned above, theprocessor 202 being coupled to an input device 204 and a display device,for example a display screen 206. Although reference is made here to theinput device 204 in the singular, the skilled person should appreciatethat the input device 204 represents any number of input devices,including a keyboard device, voice input device, touch panel and/or anyother known input device utilised to input information. Likewise, thedisplay screen 206 can include any type of display screen such as aLiquid Crystal Display (LCD), for example.

In one arrangement, one aspect of the input device 204, the touch panel,and the display screen 206 are integrated so as to provide an integratedinput and display device, including a touchpad or touchscreen input 250(FIG. 4) to enable both input of information (via direct input, menuselection, etc.) and display of information through the touch panelscreen so that a user need only touch a portion of the display screen206 to select one of a plurality of display choices or to activate oneof a plurality of virtual or “soft” buttons. In this respect, theprocessor 202 supports a Graphical User Interface (GUI) that operates inconjunction with the touchscreen.

In the navigation device 200, the processor 202 is operatively connectedto and capable of receiving input information from input device 204 viaa connection 210, and operatively connected to at least one of thedisplay screen 206 and the output device 208, via respective outputconnections 212, to output information thereto. The navigation device200 may include an output device 208, for example an audible outputdevice (e.g. a loudspeaker). As the output device 208 can produceaudible information for a user of the navigation device 200, it shouldequally be understood that input device 204 can include a microphone andsoftware for receiving input voice commands as well. Further, thenavigation device 200 can also include any additional input device 204and/or any additional output device, such as audio input/output devicesfor example.

The processor 202 is operatively connected to memory 214 via connection216 and is further adapted to receive/send information from/toinput/output (I/O) ports 218 via connection 220, wherein the I/O port218 is connectible to an I/O device 222 external to the navigationdevice 200. The external I/O device 222 may include, but is not limitedto an external listening device, such as an earpiece for example.

The connection to I/O device 222 can further be a wired or wirelessconnection to any other external device such as a car stereo unit forhands-free operation and/or for voice activated operation for example,for connection to an earpiece or headphones, and/or for connection to amobile telephone for example, wherein the mobile telephone connectioncan be used to establish a data connection between the navigation device200 and the Internet or any other network for example, and/or toestablish a connection to a server via the Internet or some othernetwork for example.

The memory 214 of the navigation device 200 comprises a portion ofnon-volatile memory (for example to store program code) and a portion ofvolatile memory (for example to store data as the program code isexecuted). The navigation device also comprises a port 228, whichcommunicates with the processor 202 via connection 230, to allow aremovable memory card (commonly referred to as a card) to be added tothe device 200. In the embodiment being described the port is arrangedto allow an SD (Secure Digital) card to be added. In other embodiments,the port may allow other formats of memory to be connected (such asCompact Flash (CF) cards, Memory Sticks™, xD memory cards, USB(Universal Serial Bus) Flash drives, MMC (MultiMedia) cards, SmartMediacards, Microdrives, or the like).

FIG. 3 further illustrates an operative connection between the processor202 and an antenna/receiver 224 via connection 226, wherein theantenna/receiver 224 can be a GPS antenna/receiver for example and assuch would function as the GPS receiver 106 of FIG. 1. It should beunderstood that the antenna and receiver designated by reference numeral224 are combined schematically for illustration, but that the antennaand receiver may be separately located components, and that the antennamay be a GPS patch antenna or helical antenna for example.

It will, of course, be understood by one of ordinary skill in the artthat the electronic components shown in FIG. 3 are powered by one ormore power sources (not shown) in a conventional manner. Such powersources may include an internal battery and/or a input for a low voltageDC supply or any other suitable arrangement. As will be understood byone of ordinary skill in the art, different configurations of thecomponents shown in FIG. 3 are contemplated. For example, the componentsshown in FIG. 3 may be in communication with one another via wiredand/or wireless connections and the like. Thus, the navigation device200 described herein can be a portable or handheld navigation device200.

In addition, the portable or handheld navigation device 200 of FIG. 3can be connected or “docked” in a known manner to a vehicle such as abicycle, a motorbike, a car or a boat for example. Such a navigationdevice 200 is then removable from the docked location for portable orhandheld navigation use. Indeed, in other embodiments, the device 200may be arranged to be handheld to allow for navigation of a user.

Referring to FIG. 4, the navigation device 200 may be a unit thatincludes the integrated input and display device 206 and the othercomponents of FIG. 2a (including, but not limited to, the internal GPSreceiver 224, the processor 202, a power supply (not shown), memorysystems 214, etc.).

The navigation device 200 may sit on an arm 252, which itself may besecured to a vehicle dashboard/window/etc. using a suction cup 254. Thisarm 252 is one example of a docking station to which the navigationdevice 200 can be docked.

The navigation device 200 can be docked or otherwise connected to thearm 252 of the docking station by snap connecting the navigation device200 to the arm 252 for example. The navigation device 200 may then berotatable on the arm 252. To release the connection between thenavigation device 200 and the docking station, a button (not shown) onthe navigation device 200 may be pressed, for example. Other equallysuitable arrangements for coupling and decoupling the navigation device200 to a docking station are well known to persons of ordinary skill inthe art.

Turning to FIG. 5, the processor 202 and memory 214 cooperate to supporta BIOS (Basic Input/Output System) 282 that functions as an interfacebetween functional hardware components 280 of the navigation device 200and the software executed by the device. The processor 202 then loads anoperating system 284 from the memory 214, which provides an environmentin which application software 286 (implementing some or all of thedescribed route planning and navigation functionality) can run. Theapplication software 286 provides an operational environment includingthe Graphical User Interface (GUI) that supports core functions of thenavigation device, for example map viewing, route planning, navigationfunctions and any other functions associated therewith. In this respect,part of the application software 286 comprises a view generation module288.

The navigation device 200 is arranged such that the user can downloadmap data into memory 214 or the memory card in card port 228. The mapdata comprises a plurality of navigable segments representing segmentsof a navigable route in the area covered by the map data, each of thenavigable segments having associated therewith a speed profile. Eachspeed profile may comprise a plurality of average speeds through thesegment for different weekly recurring time periods. The processor 202of the navigation device 200 is arranged to determine a navigable routerequested by a user using the map data and this navigable route may bebased on the speed profiles. For example, the processor 202 may use thespeed profiles to determine the fastest route and/or an estimate of thetime of travel along the route.

In the embodiment being described, the processor 202 of the navigationdevice is programmed to receive GPS data received by the antenna 224and, from time to time, to store that GPS data, together with a timestamp of when the GPS data was received, within the memory 214 to buildup a record of the location of the navigation device. Each data recordso-stored may be thought of as a GPS fix; ie it is a fix of the locationof the navigation device and comprises a latitude, a longitude, a timestamp and an accuracy report.

In one embodiment the data is stored substantially on a periodic basiswhich is for example every 5 seconds. The skilled person will appreciatethat other periods would be possible and that there is a balance betweendata resolution and memory capacity; ie as the resolution of the data isincreased by taking more samples, more memory is required to hold thedata. However, in other embodiments, the resolution might besubstantially every: 1 second, 10 seconds, 15 seconds, 20 seconds, 30seconds, 45 seconds, 1 minute, 2.5 minutes (or indeed, any period inbetween these periods). Thus, within the memory of the device there isbuilt up a record of the whereabouts of the device 200 at points intime.

In some embodiments, it may be found that the quality of the captureddata reduces as the period increases and whilst the degree ofdegradation will at least in part be dependent upon the speed at whichthe navigation device 200 was moving a period of roughly 15 seconds mayprovide a suitable upper limit.

Whilst the navigation device 200 is generally arranged to build up arecord of its whereabouts, some embodiments, do not record data for apredetermined period and/or distance at the start or end of a journey.Such an arrangement helps to protect the privacy of the user of thenavigation device 200 since it is likely to protect the location ofhis/her home and other frequented destinations. For example, thenavigation device 200 may be arranged not to store data for roughly thefirst 5 minutes of a journey and/or for roughly the first mile of ajourney.

In other embodiments, the GPS may not be stored on a periodic basis butmay be stored within the memory when a predetermined event occurs. Forexample, the processor 202 may be programmed to store the GPS data whenthe device passes a road junction, a change of road segment, or othersuch event.

Further, the processor 202 is arranged, from time to time, to upload therecord of the whereabouts of the device 200 (ie the GPS data and thetime stamp) to the server 150 via communication channel 152 includingthe wireless cellular network 300. The processor 202 is arranged toupload the record of the whereabouts on a substantially real time basis,although this may inevitably mean that data is in fact transmitted fromtime to time with a relatively short period between the transmissions,such as every 5, 10, 20, 30, 40, 50 seconds, minute, etc or any timebetween these times, and as such may be more correctly thought of asbeing pseudo real time. In such pseudo real time embodiments, thenavigation device may be arranged to buffer the GPS fixes within thememory 214 and/or on a card inserted in the port 228 and to transmitthese when a predetermined number have been stored. This predeterminednumber may be on the order of 20, 36, 100, 200 or any number in between.The skilled person will appreciate that the predetermined number is inpart governed by the size of the memory 214/card within the port 228.

In the embodiment being described, the record of the whereaboutscomprises one or more traces with each trace representing the movementof that navigation device 200 within a 24 hour period. Each 24 isarranged to coincide with a calendar day but in other embodiments, thisneed not be the case.

Generally, a user of a navigation device 200 gives his/her consent forthe record of the devices whereabouts to be uploaded to the server 150.If no consent is given then no record is uploaded to the server 150. Thenavigation device itself, and/or a computer to which the navigationdevice is connected may be arranged to ask the user for his/her consentto such use of the record of whereabouts.

The server 150 is arranged to receive the record of the whereabouts ofthe device and to store this within the mass data storage 160 forprocessing. Thus, as time passes the mass data storage 160 accumulates aplurality of records of the whereabouts of navigation devices 200 a to200 i which have uploaded data. From these records the server 150 isarranged to generate speed profiles, as now described.

As discussed above, the mass data storage 160 also contains map data.Such map data provides information about the location of road segments,points of interest and other such information that is generally found onmap.

As a first process, the server 150 is arranged to perform a map matchingfunction between the map data and the GPS fixes contained within therecords of the whereabouts that have been received and such a process isdescribed in relation to FIG. 6. Such map matching may be performed in aso-called real time manner; ie as the records of whereabouts arereceived or may be performed a time later after the records of thewhereabouts have been recalled from the mass data storage 160.

In order to increase the accuracy of the map matching, pre-processing ofthe records of the whereabouts is performed as follows. Each GPS trace(ie a 24 hour period of GPS data) is divided 600 into one or more tripswith each trip representing a single journey of the navigation device200 which are subsequently stored for later processing.

Within each trip GPS fixes whose accuracy report received from thenavigation device is not sufficiently high are rejected 602. Thus, insome embodiments, a fix may be rejected if the accuracy report indicatesthat the signals from less than three satellites 102 were being receivedby the navigation device 200 in relation to that GPS fix. Further, eachtrip is clipped 604 when the reported time between fixes goes above athreshold value. Each trip that passes this pre-processing stage ispassed to be map matched.

In this context, a clipped trip is a trip in which the there is apredetermined time period between consecutive GPS fixes of greater thana predetermined time. As such, it might be inferred that the vehicle hasremained stationary and as such it should be considered a first trip hasended and a second trip has commenced. Thus, a clipped trip becomes twoseparate trips.

However, before a trip is divided a check is made as to whether theposition of the vehicle has changed between the last two fixes since agap above the predetermined time between GPS fixes may also result froma loss of GPS signal and in such circumstances, the trip is not divided.In the embodiment being described, the predetermined time is roughly 3minutes. However, the skilled person will appreciate that the gap may beany other suitable time, such as roughly any of the following: 15seconds, 30 seconds, 1 minute, 90 seconds, 2 minutes, 5 minutes, 10minutes or any time in between these. As discussed hereinafter, if theaverage speed of a navigation device 200 from which the GPS fixes aresent is below a predetermined threshold then data, may in someembodiments, be rejected in later processing. Such an embodiment can beuseful in that it can remove data relating to so-called stop-starttraffic which occurs after incidents such as a crash or the like whichmay leave remaining data more representative of steady state trafficflow.

Then, each trip is taken in turn and fixes within that trip are matchedto a map from within the map data. Each map comprises a plurality ofroad segments along which it is possible to travel with each segmentbeing represented within the map as a straight vector.

The program code running on the processor 154 of the server 150 providesa map matcher that is arranged to step over the or each fix in the tripthat is being processed until it finds a fix which lies within a segmentor is sufficiently close to a segment in order for it to be assumed tohave occurred on that segment (ie it is within a distance threshold ofthe segment). This threshold allows for less than 100% GPS accuracy andthe compressing effect of splitting the road into a set of straightvectors.

Each trip has an initial fix (ie the first fix within the trip) which isharder to associate with a segment than other fixes within the tripsince there are no segments that have already identified which can beused to constrain the selection of the segments. If, for this first fix,multiple segments are within the threshold 606, then the algorithm looksto the next GPS fix (ie the 2nd fix) within the trip and generates a setof roots from those multiple segments based on the possible travel as afunction of the distance between the 2 fixes (ie between the 1st and 2ndfixes). If the 2nd fix does not lead to a unique candidate segment forthe 1st fix, then the algorithm moves to the 3rd fix within the trip andagain generates and compares the possible routes to try and provide aunique candidate for the first fix 608. This process may continue untilthe remaining GPS fixes within a trip have been processed.

An advantage of such an embodiment is that although any one first fix inisolation may be near multiple segments, and in isolation these segmentscan not be distinguished between, it becomes possible using the furthertravel (ie the 2nd and 3rd fixes) to determine the identity of thesegment with which the first fix is associated. Thus, a first segmentfor a trip is determined by the map matcher.

Once the first segment has been identified for a trip, further fixes areprocessed in order to identify further segments. It is of coursepossible that the next fix of the trip lies within the same segment asthe first fix 612.

Thus, the subsequent fixes of a trip are processed 610 to determine ifthey are within the distance threshold of the segment, and the mapmatcher is arranged to associate that segment with each of the fixesthat lie within the distance threshold. When the map matcher process afix that is outwith the distance threshold it is arranged to generate anew set of candidate segments for that fix. However, it is now possibleto add a further constraint that the next segment is one which isconnected to the end of the one which has just been processed. Theseneighbouring segments are obtained by the map matcher from theunderlying map data.

If at any point the map matcher fails to identify a segment for a givenfix that follows on from the previous segment, either because there areno segments within a threshold, or it cannot uniquely identify a singlesegment, then the map matcher is arranged to step through subsequentfixes 616 in order to further constrain the journey until it canidentify a segment that is a unique match. That is, if the nth fixcannot be uniquely associated with a segment the nth+1 segment is usedto further constrain the identification of a segment. If the nth+1 fixdoes not produce a unique segment then the nth+2 fix is used. In someembodiments, this process may carry on until the a unique segment isidentified or all of the GPS fixes with a trip have been processed.

The map matcher is arranged to try and uniquely identify segments; inthe embodiment being described, it does not attempt to create acontinuous route, only to try and match segments to fixes. In otherembodiments, it may be desirable to try and have the map matchergenerate continuous routes.

Therefore, at the end of the process that the map matcher is arranged toperform, a series of road segments are obtained along which thenavigation device 200 has travelled in the trip being analysed.Subsequently, the map matcher further processes these road segments andassigns, from the GPS fixes, an ingress time and also a transit time forthat segment. These assigned times are stored within the mass datastorage 160 for later processing. It may well be that a plurality of GPSfixes are stored for each road segment. However, regardless of whetherhow many GPS fixes are associated with each segment, the ingress time,GPS fixes and the length of the segment (which in this embodiment isstored within the map data) are used to calculate the average speed forthat segment of road. This average speed is then stored within the massdata storage 160 associated with the relevant assigned times and thatsegment. Information relating to a speed of traffic flow on a roadsegment and assigned to a road segment may be thought of as being speeddata for that road segment.

The server 150 is further arranged to run averaging program code on theprocessor 154 to provide an averager which processes the assigned timesto generate one or more averages therefrom as described below. Theaveraging process used in this embodiment is now described.

In a first step of the process, the averager groups the average speedsfor each road segment on the map based on the time in which that averagespeed occurred, such as the last 5 minutes, 10 minutes, 15 minutes, 30minutes, or any time in between these times.

Before an average speed generated from a trip is grouped into apredetermined time period it is screened to try and increase dataquality. In this embodiment, the average speed is only added to thegroup for the predetermined period if the average speed falls within apredetermined range. In this embodiment, the method excludes speedswhich exceed a maximum predetermined threshold (which may be roughly 180km/h) and further, the method excludes speeds which fall below apredetermined amount of the average speed for that segment in thatpredetermined time period (which may for example be 2 km/h). In otherembodiments, the max permitted speed may be set as the speed limit forthat segment of road, but the skilled person will appreciate that suchinformation can be inaccurate in map data that is being processed andalso that the speed limit for a segment of road may in fact not give anaccurate indication of traffic conditions.

A predetermined time after a set time period has passed, for example,immediately after a set time period has passed, an average speed iscalculated for each road segment for the set time period. There areseveral options for computing the average speed: using plain arithmeticor harmonic means or computing the median.

Thus, in the embodiment being described and for the map being processedthere is generated for each segment of road on the map average speedsfor the set time period that has recently passed. It will be appreciatedthat, in fact, not all road segments will necessarily have an averagespeed assigned thereto for every set time period since some roads may betraversed infrequently, particularly at unsociable times such as theearly hours of the morning.

However, before the average speeds per segment are used quality checksare performed. In some embodiments, the average is rejected if there arefewer than 5 values that went to make up that average. Other embodimentsmay of course use different values, such as 2, 3, 4, 6, 7, 8, 10, 20 ormore or any value in between these.

Also, a further check on the quality of the average is performed and foreach average the standard deviation of the average is divided by thesquare root of the number of data samples that went to make up theaverage for that segment for that time period. If the result of thiscalculation is outside a predetermined threshold then that average isagain rejected leaving a gap for that segment for that time period.

Further quality checks may be implemented to reject averages on any ofthe following: whether the deviation in the data is beyond apredetermined threshold; the existence of more than a predeterminednumber of outliers beyond a predetermined threshold. The skilled personwill appreciate such statistical techniques to ensure the quality of thedata.

The set of averages for any given road segment may be thought of as ameasured speed profile for that road segment.

The skilled person will appreciate that if a measured speed profile fora road segment has few missing speed values (ie all or at least themajority of the predetermined time periods have a value) then thatsegment may be processed and the missing values are therefore masked.

Each average that passes these quality checks is considered trustworthyand is approved for use in the map data. The server 150 then sends theseupdated speed profiles to the navigation devices 200 a to 200 i via thecommunication channel 152.

Before sending the updated speed profiles to the navigation devices 200a to 200 i, the processor of the server 150 may check to see howdifferent the updated speed profiles are from the current speed profilesof the map data being used by the navigation devices 200. If thedifference is above a predetermined threshold, then the updated speedprofile is sent to the navigation devices, however, if it is not, thenthe updated speed profile is not sent to the navigation devices. Thismay help to reduce unnecessary processing and utilization of theavailable bandwidth.

In another embodiment, the speed profiles are not average speeds througha segment during a recent set period but are delays added to the currentspeed profiles, for example the average speed of the current speedprofile minus a predicted speed differential, such as 5, 10, 15, 20, etckm/h. The predicted speed differential may be calculated usingconventional algorithms as are known to the man skilled in the art.

On receiving the updated speed profiles, the navigation device 200changes at least some of the speed profiles of the map data stored inmemory 214 or a memory card in card port 228 to the updated speedprofiles. In this way, speed profiles of the map data are updated inpseudo real time such that the map data stored on the navigation devicegives a more accurate reflection of the current traffic conditions.

If the navigation device is providing routing instructions for acalculated navigable route, the processor 202 may recalculate thenavigable route using the updated speed profiles. In this way, thenavigation device 200 may provide routes that automatically adapt tochanges in the average speed of travel through segments of a navigableroute.

In one embodiment, the processor 202 of the navigation device 200 doesnot utilise all of the updated speed profiles received from the server150 but only changes the speed profiles for segments within apredetermined distance of a current position of the navigation device200. For example, the processor 202, on receiving updated speed profilesmay identify segments within a predetermined distance of a currentposition of the navigation device and changes the speed profile for eachof the identified segments to an updated speed profile, if an updatedspeed profile has been received for that segment. The speed profiles ofsegments that fall outside the predetermined distance remain unchanged.The predetermined distance may be segments within a particular areaaround the navigation device, and in the case of a navigation devicebeing used for directing a vehicle, the predetermined distance may bebetween 50 and 200 km.

For navigation devices that are adaptable to provide navigable routesfor various forms of transport, such as walking, cycling, etc, inaddition to motor vehicles, the processor 202 of the navigation device200 may determine the predetermined distance from a current speed atwhich the navigation device is travelling. For example, thepredetermined distance may be the current speed of the navigation devicemultiplied by a preset time, for example one or more hours.

In another embodiment, the predetermined distance is based on thebandwidth for the transmission of signals between the navigation deviceand a server that provides the updated speed profile.

In this embodiment, the updated speed profiles are temporarily held inthe navigation device 200 for a predetermined length of time, such as 1hour and, after which the navigation device 200 changes the speedprofile back to the original speed profile or a further updated speedprofile. The updated speed profile determined from a recent set timeperiod may provide a better representation of the current trafficconditions for a brief period after the set time period but it is likelythat, unless further updated speed profiles are received, the originalspeed profile, which is based on average speed calculated over a numbertime periods rather than a single time period, will give a betterrepresentation of the traffic conditions at a much later times, such as1, 2 or 3 hours after the set time period.

Some embodiments perform a method of processing GPS data to generate mapdata comprising a plurality of navigable segments representing segmentsof a navigable route in an area covered by the map. FIG. 7 shows aflowchart outlining an embodiment for generating speed profiles based onprocessed GPS data. As can be seen in FIG. 7, the method comprisestransmitting GPS fixes from a plurality of navigation devices bywireless telecommunication to a processor 700. The processor thengenerates at least one speed profile for each segment from the GPS fixesfrom at least two of the plurality of navigation devices 702, each speedprofile comprising an expected speed of travel through the segment. Theprocessor next sends the speed profiles to the navigation devices bywireless telecommunications 704. In some embodiments, sending the speedprofiles comprises sending only speed profiles that differ from speedprofiles currently being used by the navigation device by more thancorresponding predetermined thresholds.

Some embodiments perform a method for determining a route across an areausing a navigation device, the navigation device comprising a wirelesstelecommunications transceiver, memory having stored thereon map datacomprising a plurality of navigable segments representing segments of anavigable route in the area covered by the map data, at least one of thenavigable segments has associated therewith a speed profile. FIG. 8shows a flowchart outlining an embodiment for using updated speedprofiles. As can be seen in FIG. 8, the method comprises calculating anavigable route using the map data 800. Next, in response to at leastone updated speed profile being received via the transceiver 802,changing, based on the at least one updated speed profile, a speedprofile for one or more segments 804. For example, the changing mayinclude identifying one or more segments within a predetermined distanceof a current position of the navigation device and changing the speedprofile for the one or more segments within the predetermined distancebased on the at least one updated speed profile, but leaving speedprofiles of segments outside the predetermined distance unchanged. Then,if the navigation device is providing routing instructions for thecalculated navigable route, recalculating the navigable route using theat least one updated speed profile 806.

The skilled person will appreciated that an apparatus provided toexecute a method as described herein may comprise hardware, software,firmware or any combination of two or more of these.

The skilled person will appreciate that, whilst the term GPS data hasbeen used to refer to position data derived from a GPS globalpositioning system as for example described in relation to FIG. 1, otherposition data could be processed in a manner similar to the methods asdescribed herein. Thus, term GPS data may be replaceable with the phrasepositioning data. Such position information could for example be derivedfrom position information derived from mobile phone operation, datareceived at toll barriers, data obtained from induction loops embeddedin roads, data obtained from number plate recognition system or anyother suitable data.

The invention claimed is:
 1. A method of operating a server comprising aprocessor and memory having map data stored thereon, said map datacomprising a plurality of navigable segments which may be selected todefine a navigable route in an area covered by the map data, at leastsome of the navigable segments having a speed profile associatedtherewith, the speed profile comprising an expected speed of travelthrough the segment for different recurring time periods, the methodcomprising: obtaining position data received by wirelesstelecommunication from a first plurality of navigation devices; causingthe processor to generate an updated speed profile indicative of currenttraffic behaviour for at least one segment by processing the positiondata from at least two of the first plurality of navigation devices; andfor each navigation device of a second plurality of navigation devices:identifying, for the navigation device, one or more segments within apredetermined distance of a current position of the navigation device;and sending, to the navigation device, updated speed profiles only forsegments identified as being within the predetermined distance.
 2. Themethod according to claim 1, wherein the speed profile associated with asegment comprises an average speed of travel of navigation devices,including the plurality of navigation devices, through the segment fordifferent recurring time periods.
 3. The method according to claim 2,wherein the updated speed profile for a segment comprises: (i) anaverage speed of travel through the segment for a time period that hasrecently passed; or (ii) a speed differential to be added to therespective average speed of the speed profile for the segment.
 4. Themethod according to claim 1, further comprising: comparing the updatedspeed profile for a segment with a respective average speed of the speedprofile for the segment to determine if a difference is above apredetermined threshold; and sending only those updated speed profilesdetermined to have a difference above the predetermined threshold forsegments identified as being within the predetermined distance.
 5. Themethod according to claim 1, wherein sending the updated speed profilesonly for segments identified as being within the predetermined distanceof the navigation device comprises skipping sending updated speedprofiles for segments that are not identified as being within thepredetermined distance of the navigation device.
 6. The method accordingto claim 1, further comprising selecting the predetermined distancebased on a distance that a corresponding navigation device may travel ina time in which the updated speed profile is relevant.
 7. The methodaccording to claim 6, further comprising selecting the predetermineddistance based at least in part on a present speed of a correspondingnavigation device.
 8. The method according to claim 1, furthercomprising selecting the predetermined distance based at least in parton a bandwidth available for sending the updated speed profiles to thesecond plurality of navigation devices.
 9. The method according to claim1, wherein at least some of the first plurality of navigation devices isincluded in the second plurality of navigation devices.
 10. Anon-transitory computer-readable medium storing computer software that,when executed on a processor of a server comprising memory having mapdata stored thereon, said map data comprising a plurality of navigablesegments which may be selected to define a navigable route in an areacovered by the map data, at least some of the navigable segments havinga speed profile associated therewith, the speed profile comprising anexpected speed of travel through the segment for different recurringtime periods, causes the server to perform a method comprising:obtaining position data received by wireless telecommunication from afirst plurality of navigation devices; causing the processor to generatean updated speed profile indicative of current traffic behaviour for atleast one segment by processing the position data from at least two ofthe first plurality of navigation devices; and for each navigationdevice of a second plurality of navigation devices: identifying, for thenavigation device, one or more segments within a predetermined distanceof a current position of the navigation device; and sending, to thenavigation device, updated speed profiles only for segments identifiedas being within the predetermined distance.
 11. A server comprisingmemory having map data stored thereon, said map data comprising aplurality of navigable segments which may be selected to define anavigable route in an area covered by the map data, at least some of thenavigable segments having a speed profile associated therewith, thespeed profile comprising an expected speed of travel through the segmentfor different recurring time periods, the server connected with awireless telecommunications transceiver configured to receive positiondata by wireless telecommunication from a first plurality of navigationdevices and send the received position data to the server, the serverfurther comprising a processor configured to: generate an updated speedprofile indicative of current traffic behaviour for at least one segmentby processing the position data from at least two of the first pluralityof navigation devices; and for each navigation device of a secondplurality of navigation devices: identifying, for the navigation device,one or more segments within a predetermined distance of a currentposition of the navigation device; and sending, to the navigation devicevia the transceiver, updated speed profiles only for segments identifiedas being within the predetermined distance.
 12. The server according toclaim 11, wherein the speed profile associated with a segment comprisesan average speed of travel of navigation devices, including theplurality of navigation devices, through the segment for differentrecurring time periods.
 13. The server according to claim 12, whereinthe updated speed profile for a segment comprises: (i) an average speedof travel through the segment for a time period that has recentlypassed; or (ii) a speed differential to be added to the respectiveaverage speed of the speed profile for the segment.
 14. The serveraccording to claim 11, wherein the processor is further configured to:compare the updated speed profile for a segment with a respectiveaverage speed of the speed profile for the segment to determine if adifference is above a predetermined threshold; and send only thoseupdated speed profiles determined to have a difference above thepredetermined threshold for segments identified as being within thepredetermined distance.
 15. The server according to claim 11, whereinsending the updated speed profiles only for segments identified as beingwithin the predetermined distance of the navigation device comprisesskipping sending updated speed profiles for segments that are notidentified as being within the predetermined distance of the navigationdevice.
 16. The server according to claim 11, wherein the processor isconfigured to select the predetermined distance based on a distance thata corresponding navigation device is predicted to may travel in a timein which the updated speed profile is relevant.
 17. The server accordingto claim 16, wherein the processor is configured to select thepredetermined distance based at least in part on a present speed of acorresponding navigation device.
 18. The server according to claim 11,wherein the processor is configured to select the predetermined distancebased at least in part on a bandwidth available for sending the updatedspeed profiles to the second plurality of navigation devices.
 19. Theserver according to claim 11, wherein at least some of the firstplurality of navigation devices is included in the second plurality ofnavigation devices.